100 Questions on Basic Electroplating Knowledge (Part 3)

11. How does pre-treatment before plating affect the quality of the electroplated layer?

Answer: Long-term production practice has proved that most of the quality accidents in electroplating production are not caused by the electroplating process itself. They are mostly due to improper pre-treatment of metal products. Especially the smoothness, adhesion, and corrosion resistance of the electroplated layer are closely related to the quality of pre-treatment. The surface condition and cleanliness of metal products before electroplating are important links to obtaining high-quality electroplated layers. On rough metal surfaces, it is difficult to obtain smooth and bright electroplated layers, and the electroplated layers have more pores, reducing their anti-corrosion performance. If there is any oil or dirt on the metal surface, normal electroplated layers cannot be obtained.

12. What is the definition of free cyanide in cyanide plating solutions?

Answer: In cyanide plating solutions, the excess cyanide not combined in complex salts is called free cyanide. For example, in cyanide copper plating solutions, free cyanide is the cyanide that is not part of the [Cu(CN)3]= complex ion.

13. In cyanide copper plating, when the anode becomes passivated and dissolves poorly, why does the content of free cyanide increase?

Answer: During cyanide copper plating, if the anode dissolves poorly, although some cyanide ions are oxidized and consumed at the anode, more free cyanide ions are produced at the cathode due to the discharge of copper cyanide complex ions, thus increasing the content of free cyanide in the plating solution.

14. How does the anode material affect the quality of the electroplated layer in acid bright copper plating?

Answer: In acid bright copper plating processes, if electrolytic copper anodes are used, copper powder is easily produced, causing rough electroplated layers and rapid consumption of brighteners. Therefore, copper anodes containing a small amount of phosphorus (0.1-0.3%) should be used to significantly reduce copper powder. However, if copper anodes with too high phosphorus content are used, the anode dissolution performance will deteriorate, causing the copper content in the plating solution to decrease.

15. In nickel plating solutions, when the anode area decreases and the anode current density increases, does the pH value of the solution rise or fall?

Answer: The pH value of the solution decreases. This is because when the anode area decreases and the current density increases, the anode becomes passivated and does not dissolve. After passivation, oxygen is released, increasing the H+ ions in the solution and thus increasing the acidity, causing the pH to drop.